A conventional exercise device such as elliptical exerciser or stair climbing exerciser include two pedals which are respectively connected to two respective operation rods. A distal end of each of the operation rods is connected to an arm which can be pivoted reciprocally when the feet of a user step on the two pedals. The trace of the two pedals is an oval path such that the muscles of the feet can be exercised during the operation. The pedals are made large enough so as to fit different users needs and the larger the pedal is, the higher manufacturing cost is required. The mold for making the pedals has to be bulky and the travel of the plastic injection machine is also long, both of the two factors affect the cost of the manufacture. The number of the pedals that one process of plastic injection can produce is limited because of the size of the pedals and the cooling period is increased between two adjacent injections.
The present invention intends to provide a pedal structure wherein the pedal can be adjusted along the operation rod according different needs.